Distribution of lithium and fluorine in lujavrites from the Ilímaussaq intrusion

Abstract

The development of a relatively rapid neutron activation technique, involving fast transfer of samples from the reactor followed by Cerenkov counting, has allowed us to extend the analytical coverage of Li and F in the Ilimaussaq lujavrites and their minerals. On geological grounds the lujavrites have been regarded as crystallising from the final agpaitic magmas at Ilimaussaq. In agreement with this, contents of Li and F - which are normally maximal in residual magmas - have been shown to attain their highest levels within the lujavrites (Gerasimovsky, 1969; Ferguson, 1970). However, these studies failed to agree on the absolute contents of Li in the lujavrites. For aegirine lujavrite and arfvedsonite lujavrite, Gerasimovsky (1969) reported averages of 155 and 791 ppm, respectively, whereas Ferguson (1970) found only 90 and 226 ppm. Hamilton (1964) only reported 80 ppm Li in a single sample of arfvedsonite lujavrite.